Chinese proclamations on coal consumption and the corresponding decline in carbon emissions may be off the mark, a journal study found.

A recent report from the Brookings Institution stated coal use in China may have peaked and is starting to slow down as the country shifts from an economic strategy of quantitative growth to one geared to quality. Coal consumption, the report said, declined last year after dropping 2.4 percent in 2014, part of what researchers at Brookings said was a long-term trend.

Researchers from Center for International Climate and Environmental Research - Oslo, or CICERO, whose article was published in the journal Nature Communications, found Chinese energy data are often plagued by "large anomalies" and characterized by a high degree of uncertainty.

When British energy company BP reviewed Chinese data, it found emissions of carbon dioxide, a potent greenhouse gas, increased 0.9 percent when official data showed a 1.5 percent drop in response to a decline in reported coal consumption.

When the country reported a 2.9 percent decline in coal consumption in 2014, it was hailed as a breakthrough given the country's track record for economic growth. The journal study noted Chinese coal consumption data are revised alongside census statistics.

"We show that the preliminary 2.9 percent reduction in coal consumption is inappropriate for estimating CO2 emissions, that coal-derived energy consumption stayed flat but is likely to have decreased in 2015, and that Chinese fossil CO2 emissions probably increased about 0.8 percent in 2014," the journal report read.

A National Economic and Social Development plan outlined by the Chinese government in early March described a series of measures aimed at controlling air, water and soil pollution.

Coal-based heating and industrial activity in Beijing are key contributors to the air pollution. The five-year plan calls for stricter rules on energy conservation and a stronger focus on industries associated with environmental protection.